Matter and Bonding
1. Understand the atomic models of Dalton, Thompson and Bohr-Rutherford.
a. Dalton Atomic Model: The ‘Billiard Ball’ Model
* All matter is made up of tiny particles called atoms.
* All atoms of the same element are the same in mass and volume.
* Atoms of different elements combine in small whole number ratios to form new compounds.
b. Thompson Atomic Model: The ‘Chocolate Chip Cookie’ Model
* The discovery of electrons: cathode ray tubes
* The atom is a solid ball of positive charge with
negatively charged electrons embedded in it.
* The amount of positive charge equals the amount of negative charge, so the entire atom is neutral.
...view middle of the document...
12 | 1+ | In the nucleus |
Neutron | 1838.65 | 0 | In the nucleus |
3. Outline trends on the periodic table.
a. Atomic Radius: the distance from the centre of the atom to the outermost shell that contains electros
↓ increasing atomic radius | → decreasing atomic radius |
Why: number of shells increased | Why: the nuclear charge increases; strength of attraction between nucleus and valence electrons increase as protons are added |
b. Ionization Energy: the amount of energy (kJ) that is required to remove one of the outermost electrons from the atom in a gaseous state. The energy to strip an electron from an atom.
↓ decreasing ionization energy | → increasing ionization energy |
Why: the bigger the radius, the more energy shells: the further shells have less gravitational pull, and it is easy for this atom to lose its electrons | Why: higher ionization energy atoms have an almost full shell and it is easier to gain electrons; a higher nuclear charge (atoms get smaller): nucleus and valence electrons attractions are increases (more secured valence electrons) |
c. Electrongativity: a measure of the ability of the atom to attract an electron from another atom. If an atom is really good at ‘stealing’ electrons from another atom then it has a high electronegativity value. The numbers range from 0.5-4.0 (Fluorine). The ‘Noble Gases’ do not have electronegativity values, since they are already stable.
↓ decreasing elctronegativity | → increasing electronegativity |
Why: further shells have less gravitational pull and more likely to lose electrons |
4. Be able to classify compounds as ionic or covalent in nature. Give properties of ionic substances and contrast these with properties of covalent substances.
Ionic compounds: a pure substance formed from a metal and a non-metal; metal and polyatomic ion. Held together by attractive forces; positive-negative.
* Remember multivalent metals: metals with more than 1 possible charge.
Molecular compounds: a pure substance formed from 2 or more different non-metals
* Covalent bond: the attractive force between 2 atoms that results when electrons are shared by the atoms; a type of chemical bond
* Diatomic molecule: a molecule consisting of 2 atoms of the same or different elements
| Molecular (Covalent) | Ionic |
Example | Table Sugar | Table Salt |
Composition | Made up of molecules | Made up of repeating formula units, which form a crystal lattice. Each ion has a position in the lattice that maximized the attractive forces and minimizes contact with similarly charged ions. |
State at SATP | Gas, liquid, or solid | Usually solid |
Melting/Boiling Points | LOW | HIGH |
Hardness of crystalline solids | Solids are soft and waxy (e.g. candle wax) | Solids are hard and brittle |
Solubility in water | Range in solubility (e.g. sugar dissolves; wax doesn’t) | Soluble in water (dissolves) |
Conductivity in water | Non-electrolyte | Electrolyte |